Inverter system and control system for electric vehicle

Abstract

An inverter system providing both an improvement in the voltage utilization factor and a reduction in the switching loss uses a two-phase switching method. In the inverter system, an α-axis voltage command value; v.sub.αr and a β-axis voltage command value v.sub.βr are input to a stop phase selection means. Six sections are judged based on the values v.sub.αr and v.sub.βr to select phases for which it is allowable to stop pulse width modulation control in a two-phase switching method. Then, a phase having the largest absolute value of current is selected among the phases for which it is allowable to stop pulse width modulation control using a U-phase current i u and a V-phase current i v . This information is a control mode S. Based on these, two-phase switching calculations are performed by a dead-time compensation calculation means and a pulse width modulation generating means. By doing so, the switching loss can be reduced.

We claim: 
     
       1. An inverter system comprising inverters for supplying electric power to a multi-phase load according to pulse width modulation signals, and a controller for controlling said inverters while stopping a pulse width modulation signal of any one phase of said multi-phase load, wherein said controller controls said inverters by selecting a plurality of phases for which said pulse width modulation signals are allowed to stop, and stopping a pulse width modulation signal corresponding to a phase having the largest phase current among said selected plurality of phases, and   wherein said phase current is estimated based on a current command value to be supplied to said load.   
     
     
       2. An inverter system comprising inverters for supplying electric power to a multi-phase load according to pulse width modulation signals, and a controller for controlling said inverters while stopping a pulse width modulation signal of any one phase of said multi-phase load, wherein said controller comprises voltage compensation means which stops a dead-time compensation for said phase for which supply of said pulse width modulation signal is stopped, and applies a dead-time compensation voltage to other phases, said dead-time compensation voltage being determined on the basis of a direction of a current of each of said other phases. 
     
     
       3. An inverter system comprising inverters for supplying electric power to a multi-phase load according to pulse width modulation signals, and a controller for controlling said inverters with said pulse width modulation signals, wherein said controller comprises switching means for switching between a circuit for controlling all of the phases by said pulse width modulation signals and a circuit for controlling the inverters while at least one pulse width modulation signal to at least one phase is being stopped.   
     
     
       4. An electric vehicle control system comprising an induction motor for driving the vehicle, an inverter system for controlling said induction motor, and a controller for generating pulse width modulation signals to be input to said inverter system in response to a current command value for said induction motor, wherein said controller drives said induction motor with a reduced field control, and stops at least one pulse width modulation signal of at least one phase among said pulse width modulation signals.   
     
     
       5. An electric vehicle control system according to claim 4, wherein said phase of which the pulse width modulation signal is stopped is delayed by 30 degrees from a pre-set reference phase-angle when said induction motor is in a power driving state and is advanced by 30 degrees from said reference phase-angle when the induction motor is in a regeneration state. 
     
     
       6. An electric vehicle control system comprising a synchronous motor for driving the vehicle, an inverter system for controlling said synchronous motor, and a controller for generating pulse width modulation signals to be input to said inverter system from any one of a current command value to be conducted to and a voltage command value to be applied to said synchronous motor, wherein said controller performs field control of said synchronous motor, and stops at least one pulse width modulation signal of one phase among said pulse width modulation signals.   
     
     
       7. An electric vehicle control system according to claim 6, wherein said phase for which said pulse width modulation signal is stopped is determined based on a voltage to be applied to said synchronous motor. 
     
     
       8. An electric vehicle control system according to claim 7, wherein said controller estimates said voltage based on said voltage command value. 
     
     
       9. An electric vehicle control system according to any one of claim 4 or claim 6, wherein said controller performs field control so that a power factor of the motor becomes 0.86 or more. 
     
     
       10. An electric vehicle control system according to claim 9, wherein said phase for which said pulse width modulation signal is stopped is determined based on a magnitude of a current flowing to said motor. 
     
     
       11. An electric vehicle control system according to claim 10, wherein said controller estimates said magnitude of current based on said current command value.